Bind to an Item of a Dependency Collection - xaml

Question

I'm trying to create a custom control that has a header and a footer and body. The idea is that the body of the report is a custom stack panel control that will allow the user to indicate page orientation and grouping. I created a dependency property on the custom UC to accept an IList of the custom stack panel. What I am trying to do is bind to one of the stack panels in the list. But for some reason the binding is not working.
The ReportPage:
public class ReportPage : StackPanel
{
//Nothing right now but will eventually include controls for page orientation and size (8.5x11, 11x17, etc.)
}
The UserControl code behind:
public partial class Report : UserControl, INotifyPropertyChanged
{
public Report()
{
ReportPages = new List<ReportPage>();
}
public static readonly DependencyProperty =
DependencyProperty.Register("ReportPages", typeof(IList), typeof(Report));
public IList ReportPages
{
get => (IList)GetValue(ReportPagesProperty);
set
{
SetValue(ReportPagesProperty, value);
ActivePage = value[0];
OnPropertyChanged(nameof(ActivePage));
}
}
private ReportPage _activePage;
public ReportPage ActivePage
{
get => _activePage;
set
{
_activePage = value;
OnPropertyChanged(nameof(ActivePage));
}
{
}
The UserControl xaml:
<Grid>
<!--Some xaml for the header and footer.-->
<ContentControl Content="{Binding ActivePage, RelativeSource={RelativeSource, FindAncestor, AncestorType=local:Report}}"/>
</Grid>
Here is how I am consuming the custom control. This should, in my mind at least, make three "pages" which I can toggle between using a button control that I didn't share.
<reportEngine:Report>
<reportEngine:Report.ReportPages>
<reportEngine:ReportPage>
<TextBlock>This is Page 1</TextBlock>
</reportEngine:ReportPage>
<reportEngine:ReportPage>
<TextBlock>This is Page 2</TextBlock>
</reportEngine:ReportPage>
<reportEngine:ReportPage>
<TextBlock>This is Page 3</TextBlock>
</reportEngine:ReportPage>
</reportEngine:Report.ReportPages>
</reportEngine:Report>
Any Ideas why the binding isn't working?

Answer 1

So I at least found a quick work around. I utilized the Collection Changed Event handler pattern from this answer and modified it for static dependency properties. Then, to get the values from the collection bound to the dependency property I create a static instance of the Report object in the constructor and use that to pass various values back to the object from the collection. Something like this:
public partial class Report : UserControl, INotifyPropertyChanged
{
private static Report _thisReport;
public Report()
{
InitializeComponent();
ReportPages = new ObservableCollection<ReportPage>();
_thisReport = this;
}
public static readonly DependencyProperty ReportPagesProperty =
DependencyProperty.Register("ReportPages", typeof(IList), typeof(Report), new FrameworkPropertyMetadata(ReportPagesChanged));
public IList ReportPages
{
get => (IList)GetValue(ReportPagesProperty);
set
{
SetValue(ReportPagesProperty, value);
//Update some other properties associated with the control (Total Page Numbers, etc.)
}
}
private static void ReportPagesChanged(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs eventArgs)
{
var newColl = (INotifyCollectionChanged)eventArgs.NewValue;
if (newColl != null)
newColl.CollectionChanged += ReportPages_CollectionChanged;
var oldColl = (INotifyCollectionChanged)eventArgs.OldValue;
if (oldColl != null)
oldColl.CollectionChanged -= ReportPages_CollectionChanged;
}
private static void ReportPages_CollectionChanged(object sender, NotifyCollectionChangedEventArgs eventArgs)
{
var newPages = (IList<ReportPage>) sender;
//Updates properties of the Report control.
_thisReport.ActivePage = newPages[0];
_thisReport.TotalPageNumber = newPages.Count;
}
}
Whether this is "correct" or not I couldn't say, but it works. If someone has a better answer I will change the answer.